Azido-PEG1-CH2CO2-NHS

Azido-PEG1-CH2CO2-NHS is a multifunctional polyethylene glycol-based PROTAC linker designed to enable modular assembly through orthogonal chemistries. Its azide handle supports bioorthogonal conjugation, while the NHS ester provides efficient amide-bond formation with primary amines. The PEG segment improves aqueous solubility and can enhance effective linker flexibility in targeted protein degradation workflows. Detailed structural and reactivity considerations for PROTAC construction are provided below.

Structure: The linker contains a terminal azide for click-type reactivity and an NHS ester for acyl transfer to amines, connected through a short PEG chain and a methylene spacer. It features ether linkages within PEG, an activated carboxylate, and stable covalent bonds suitable for stepwise conjugation in aqueous media.

Reactivity: The NHS ester reacts with primary amines via nucleophilic acyl substitution to form stable amide bonds, typically under mildly basic conditions that preserve NHS reactivity while minimizing hydrolysis. The azide can participate in azide–alkyne cycloaddition or related azide-compatible conjugation strategies, often using appropriate catalysts or catalyst-free systems depending on the partner. Common solvents include aqueous buffers with controlled ionic strength; freshly prepared solutions and timely coupling are recommended to limit ester hydrolysis.